chore: Flutter mobile app, CI, and dev tooling

- mobile/: Flutter/Dart merchant mobile app skeleton
- .github/: GitHub Actions CI workflows
- .dockerignore: exclude host node_modules from build context
- .cursorrules: Cursor IDE project rules
- .claude/: Claude Code project settings and launch config

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

mobile/meezi_pos/lib/features/pos/pos_screen.dart

@@ -0,0 +1,16 @@
+import 'package:flutter/material.dart';
+
+/// Phase 1: online POS shell. Phase 2: Drift cart + sync queue + bluetooth_print.
+class PosScreen extends StatelessWidget {
+  const PosScreen({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(title: const Text('صندوق')),
+      body: const Center(
+        child: Text('POS — منو و سبد در فاز بعدی (Drift + API)'),
+      ),
+    );
+  }
+}